when the wave encounters an interface between two
media.
The propagation of a wave depends on the properties of the medium or region through which the wave travels. The speed of a wave, including electromagnetic waves such as light, depends on the material through which it travels. When light (or any other type of wave) travels from one material to another, the frequency remains the same, but the change in wave speed causes a change in the propagation direction, described by Snell’s law. This change in direction is termed refraction when light passes through an interface. Reflection occurs when part or all of a wave bounces back from the interface. Both reflection and refraction can be used to form images. The study of image formation with light is called geometrical optics and involves the properties of images formed with mirrors and lenses.
Essential Knowledge 6.E.1: When light travels from one
medium to another, some of the light is transmitted, some is reflected, and some is absorbed. (Qualitative
understanding only.) ph y s ic s 2
Learning Objective 6.E.1.1:
The student is able to make claims using connections across concepts about the behavior of light as the wave travels from one medium into another, as some is transmitted, some is reflected, and some is absorbed.
[See Science Practices 6.4 and 7.2]
Essential Knowledge 6.E.2: When light hits a smooth reflecting
surface at an angle, it reflects at the same angle on the other side of the line perpendicular to the surface (specular reflection); this law of reflection accounts for the
size and location of images seen in mirrors. p
h y s ic s 2
Learning Objective 6.E.2.1:
The student is able to make predictions about the locations of object and image relative to the location of a reflecting surface. The prediction should be based on the model of specular reflection with all angles measured relative to the normal to the surface. [See Science Practices 6.4 and 7.2]
Essential Knowledge 6.E.3: When light travels across a boundary
from one transparent material to another, the speed of propagation changes. At a non-normal incident angle, the path of the light ray bends closer to the perpendicular in the optically slower substance. This is called refraction. a. Snell’s law relates the angles of incidence and
refraction to the indices of refraction, with the ratio of the indices of refraction inversely proportional to the ratio of the speeds of propagation in the two media. b. When light travels from an optically slower substance
into an optically faster substance, it bends away from the perpendicular.
c. At the critical angle, the light bends far enough away from the perpendicular that it skims the surface of the material.
d. Beyond the critical angle, all of the light is internally reflected. p h y s ic s 2
Learning Objective 6.E.3.1:
The student is able to describe models of light traveling across a boundary from one transparent material to another when the speed of propagation changes, causing a change in the path of the light ray at the boundary of the two media.
[See Science Practices 1.1 and 1.4]
Learning Objective 6.E.3.2:
The student is able to plan data collection strategies as well as perform data analysis and evaluation of the evidence for finding the relationship between the angle of incidence and the angle of refraction for light crossing boundaries from one transparent material to another (Snell’s law).
[See Science Practices 4.1, 5.1, 5.2, and 5.3]
Learning Objective 6.E.3.3:
The student is able to make claims and predictions about path changes for light traveling across a boundary from one transparent material to another at non-normal angles resulting from changes in the speed of propagation.
Essential Knowledge 6.E.4: The reflection of light from surfaces
can be used to form images.
a. Ray diagrams are very useful for showing how and where images of objects are formed for different mirrors and how this depends upon the placement of the object. Concave and convex mirror examples should be included. b. They are also useful for determining the size of the
resulting image compared to the size of the object. c. Plane mirrors, convex spherical mirrors, and
concave spherical mirrors are part of this course. The construction of these ray diagrams and comparison with direct experiences are necessary.
p h y s ic s 2
Learning Objective 6.E.4.1:
The student is able to plan data collection strategies and perform data analysis and evaluation of evidence about the formation of images due to reflection of light from curved spherical mirrors. [See Science Practices 3.2, 4.1, 5.1, 5.2, and 5.3]
Learning Objective 6.E.4.2:
The student is able to use quantitative and qualitative representations and models to analyze situations and solve problems about image formation occurring due to the reflection of light from surfaces. [See Science Practices 1.4 and 2.2]
Essential Knowledge 6.E.5: The refraction of light as it travels from one
transparent medium to another can be used to form images. a. Ray diagrams are used to determine the relative size
of object and image, the location of object and image relative to the lens, the focal length, and the real or virtual nature of the image. Converging and diverging lenses should be included as examples.
p h y s ic s 2
Learning Objective 6.E.5.1:
The student is able to use quantitative and qualitative representations and models to analyze situations and solve problems about image formation occurring due to the refraction of light through thin lenses.
[See Science Practices 1.4 and 2.2]
Learning Objective 6.E.5.2:
The student is able to plan data collection strategies, perform data analysis and evaluation of evidence, and refine scientific questions